The Obama administration called Russia’s advances in Ukraine “a brazen act of aggression” Sunday and threatened sanctions but skirted questions about whether the United States might use force to deter Russian President Vladimir Putin.

The State Department announced Sunday that Secretary of State John F. Kerry will visit Kiev on Tuesday to show support for the new leadership there in the face of the Russian military intervention. Kerry on Sunday called the rapid movement of Russian troops across the border into Ukraine’s Crimea region unwarranted and outside international law and said Russia would suffer economic and political consequences.

“He’s going to lose on the international stage,” Kerry said on NBC’s “Meet the Press,” referring to Putin. “Russia is going to lose, the Russian people are going to lose, and he’s going to lose all of the glow that came out of the Olympics, his $60 billion extravaganza.”

Economic sanctions and travel restrictions on individual Russians are one possibility, as is a U.S. and European boycott of planning meetings this week for the upcoming summit of the Group of Eight leading industrial nations in Russia.

The United States, Britain, Canada, France, Germany, Italy, Japan and Russia are members of the G-8.

“There are visa bans, asset freezes, isolation with respect to trade, investment,” Kerry said on CBS’s “Face The Nation.” “American businesses may well want to start thinking twice about whether they want to do business with a country that behaves like this. These are serious implications.”

Kerry also said that the administration was ready to provide economic assistance “of a major sort” to Ukraine.

President Obama discussed Ukraine on Sunday with the leaders of Germany, Britain and Poland.

Administration officials said the trade and economic penalties being considered would target Russia’s prized economic position abroad. Actions against Russian banks are a possible avenue, one administration official said, while another said the potential actions would be significant and would leave Russia weaker.

“This will have a cost on the Russian economy,” one senior administration official said, speaking on the condition of anonymity to describe the unfolding international diplomacy. “Some of those costs will be imposed by the United States; some of that Russia has already invited on itself,” the official added.

The official acknowledged that efforts are “focused on political and economic options.”

The situation in Ukraine escalated rapidly over the weekend, with thousands of Russian troops entering Crimea and capturing the Black Sea peninsula without firing a shot. Obama implored Putin to step back during a 90-minute telephone conversation Saturday that the White House described as the toughest of his presidency.

Russian forces surrounded a Ukrainian army base Sunday, and Ukraine began mobilizing its military in response.

Ukrainian Prime Minister ­Arseniy Yatsenyuk warned, “We are on the brink of disaster.”

“We believe that our Western partners and the entire global community will support the territorial integrity and unity of Ukraine,” the former opposition leader said Sunday in Kiev.

Kerry said that he spoke Saturday with foreign ministers from the G-8 and other nations and that “every single one of them are prepared to go to the hilt in order to isolate Russia.”

“They’re prepared to put sanctions in place,” he said. “They’re prepared to isolate Russia economically. The ruble is already going down. Russia has major economic challenges. I can’t imagine that an occupation of another country is something that appeals to a people who are trying to reach out to the world, and particularly if it involves violence.”

Despite widespread outrage, the United States and other Western nations struggled to show how the mostly symbolic penalties under consideration would help the new leadership in Ukraine fend off Russia or hold on to the restive, Russian-oriented Crimean Peninsula.

“The last thing anybody wants is a military option,” Kerry said. “We want a peaceful resolution through the normal processes of international relations.”

Military force is always an option, U.S. officials said.

“I won’t get into the different specific options, but this could be a very dangerous situation if this continues in a very provocative way,” Defense Secretary Chuck Hagel said on “Face The Nation.” “We have many options, like any nations do. We’re trying to deal with the diplomatic focus. That’s the appropriate, responsible approach, and that’s what we’re going to continue.”

Sen. Marco Rubio (R-Fla.), a member of the Senate Foreign Relations Committee, said there is no broad call to arms.

“If you’re asking me whether the U.S. should be taking military strikes against Russian troops in Ukraine or in Crimea, I would argue to you that I don’t think anyone is arguing for that,” he said on NBC.

Unlike in 2008, when Russian troops entered neighboring Georgia, there were no immediate signs that the United States or other nations were positioning military forces or equipment in response. The conflict with U.S.-backed Georgia, like Ukraine a former Soviet republic, brought Washington’s relations with Moscow to a new low. Nearly six years later, Russian troops remain in Georgia.

Obama’s first-term “reset” with Russia was supposed to help ease tension over Georgia and over U.S. plans to field a missile defense system in Poland and other nations at Russia’s doorstep. Diplomatic gestures such as smoothing Russia’s entry into the World Trade Organization were supposed to help, as was the decision to hold the G-8 meeting in Sochi, site of the recent Winter Olympics.

Sen. Lindsey O. Graham (R-S.C.) suggested suspending Russia’s membership in the G-8 for at least a year, “starting right now.”

“Let’s challenge him where we can,” Graham said of Putin.

In Brussels, NATO chief ­Anders Fogh Rasmussen said Russia had violated the U.N. Charter by moving on Ukraine. The alliance’s political decision-making body held crisis talks Sunday.

Ukraine has taken part in some NATO exercises but is not an alliance member. That means the United States and Europe are not obligated to come to its defense.

“It is very important that we all do everything we can to calm tensions,” said British Foreign Secretary William Hague, who flew to Kiev on Sunday. “The Ukrainians have said to me in the last couple of days that they will not rise to provocations.”

China’s Foreign Ministry posted a statement on its Web site Sunday evening condemning what it called “recent acts of extreme violence in Ukraine.”

Spokesman Qin Gang urged “all parties concerned in Ukraine to resolve their internal dispute within the legal framework, and earnestly protect the legal rights and interests of all Ukrainian people to restore normal social order as soon as possible.”

Broader international action through the United Nations is unlikely because Russia holds veto power as a permanent member of the Security Council.

Ukraine’s ambassador to the United Nations, Yuriy Sergeyev, appeared to acknowledge that if the conflict escalates into a shooting war, outside military help would probably be limited to weapons or other aid short of foreign forces.

“We are preparing to defend ourselves,” Sergeyev told CNN, adding, “Naturally, we will ask for military support and other kind of support” if Russia continues to escalate its forces.

Kerry appealed to Putin’s desire for respect and international legitimacy, saying the rest of the world would be forced to isolate Russia if it broke the rules. Kerry said that Putin and Russia have many options short of invasion to address legitimate concerns about the future of Russian speakers in Ukraine and that the United States is prepared to help sort through them. But he added a few digs at Putin.

“Russia chose this brazen act of aggression and moved in with its forces on a completely trumped-up set of pretexts, claiming that people were threatened,” Kerry said on CBS. “And the fact is that that’s not the act of somebody who is strong. That’s the act of somebody who is acting out of weakness and out of a certain kind of desperation.”

Putin’s office issued a statement saying that “Russia retains the right to protect its interests and the Russian-speaking population” in eastern Ukraine.

William Wan in Beijing and Jaime Fuller in Washington contributed to this report.